This invention relates to heat exchangers, and in particular to heat exchangers made up of stacked plate pairs defining flow passages therebetween.
As well known in the art, vehicle fuel systems, for example those used in diesel passenger vehicles, often require a fuel to air cooler to cool excess fuel that is returned to the fuel tank from the fuel system. Due to limited space and high ambient temperatures, it is generally not practical to locate a fuel cooler in the engine compartment of a vehicle. Instead, it is often possible to locate the fuel cooler in an external location under the body of the vehicle. For example in a passenger vehicle, the fuel cooler may be located under the floor pan.
Generally, there is very limited space to put an underbody mounted cooler in. For example, in a passenger vehicle, the entire available space for an under-the-floor-pan cooler may be a height of about 35 mm, a length of 1-2 meters and a width of about 120 mm. Thus, it is important for an underbody cooler to be compact and have high heat exchange efficiency. Additionally, as an underbody cooler is exposed to debris and other objects, it must be very durable.
Current under-body fuel coolers generally fall into two categories, namely serpentine tube on plate coolers and extrusion type coolers. Serpentine tube on plate coolers consist of a serpentine tube bonded (brazed) to an aluminum plate. The plate may have lanced louvers, which serve to interrupt the air flow boundary layer. Extrusion type coolers include an aluminum finned-portion that is co-extruded with an adjacent flow channel portion. After extrusion, the flow channel portion is closed off at opposite ends and inlet and outlet fittings provided. Underbody mounted fuel coolers typically have low fuel mass flow velocities and speed dependent air mass flows, and are—in terms of heat transfer—typically “airside limited”. Extrusion-type coolers typically suffer from limited air flow mixing (i.e. disrupting the airside heat transfer boundary layer). Serpentine tube on plate coolers typically suffer from limited air flow mixing and a relatively low airside heat transfer area.
In addition to extrusion-type and serpentine tube on plate coolers, an alternative form of heat exchanger is the stacked plate-pair heat exchanger as is shown, for example, in U.S. Pat. No. 5,692,559 issued Dec. 2, 1997, and assigned to the assignee of the present invention. Stacked plate pair heat exchangers are typically cost efficient to manufacture and have been widely adopted for applications such as oil coolers. However, existing stacked-plate pair heat exchangers have generally not been configured for use as under-body heat exchangers.
It is therefore desirable to provide a stacked plate pair heat exchanger that is configured for use as an underbody cooler and which provides improved air-flow mixing and heat transfer area.